Since its invention over a century ago, the telephone has become an essential tool of modern life. A tremendous amount of business, both commercial and personal, is conducted over the telephone in developed countries throughout the world.
However, as most people who conduct a large amount of their commercial business over the telephone are aware, the telephone is a mixed blessing of modern life. Many people after spending several days on the telephone at the office find it extremely annoying to have the telephone ringing at home in the evening. In order to isolate themselves from the telephone, many people have adopted expedients such as taking the telephone off-hook, disconnecting the telephone, and having all calls screened by an answering machine.
Furthermore, there are many circumstances in daily life in which the user of a telephone set desires to know when an incoming call is present on the line but for which the provision of an audible ringing signal can be extremely problematic. For example, if one has just successfully coaxed a fussy baby into going to sleep, the ringing of the telephone can reawake the child, compounding the general audible commotion within the home. Similarly, if one is engaged in recording or listening to live music, the sound of a telephone ringing interrupting such activity can be extremely annoying.
Conversely, many people can be in situations in which they wish to be alerted to the ringing of the telephone but in which the prevailing conditions make this difficult or impossible. For example, apartment dwellers who are also afficianadoes of loud music, often use headphones as a listening device. Extremely high sound pressure levels can be created within the confines of the headphone and it is often impossible for a person engaging in this activity to hear the ringing of the telephone. Also, the dial up telephone network is commonly used by hearing impaired or deaf people to communicate through forms of teletype machines. It is necessary to provide deaf but sighted people with a visual indication that the phone is ringing. There are also many industrial locations where high ambient noise levels make visual signaling for a ringing telephone desirable.
The present inventor is aware of prior art visual indicators responsive to the presence of a ringing signal on a telephone line. The context in which these devices have been seen is in arrangements for providing telecommunications for deaf people. Such specialized arrangements for deaf people normally include some form of incandescent lamp which is constantly or intermittently lighted in response to the presence of a ringing signal on a telephone line. This will normally be one of several lamps distinguishable by pulsing characteristic or color used to signal deaf people of the presence of signals which are normally provided as audible signals for persons with normal hearing. For example, the equivalent of the door bell in the house of a deaf person may be implemented in the form of turning on a light of a different color than the light which indicates the ringing of the telephone.
To the best of the inventor's knowledge, the prior art arrangements for providing visual indications that a ringing signal is present on a telephone line have included illumination devices provided with separate power sources and circuitry which corresponds to a conventional ring detect circuit such as might be used in a voice connecting arrangement for PBX to trigger illumination of the externally powered device. Devices of this type have also been used in high noise industrial environments.
Also, as most travelers are aware, many telephone sets on room extensions of hotel and motel private branch exchanges are equipped with a "message light". Many such arrangements for hotel message lights include polarity sensitive circuitry connected so that application of reverse battery supervision will cause the lamp to become constantly illuminated. Other arrangements have included ones for which breakdown devices (which may be external or may be embodied in the form of a neon lamp used for the message light) are used and the application of additional DC voltage to the extension line causes the lamp to become illuminated.
Under either of these circumstances, the common experience of most people is that the message lamps on such phone sets will flicker when the telephone rings. This normally occurs at a pulse repetition rate equal to the frequency of the ringing signal, or the frequency of the envelope of the ringing signal. Alternately, current in lamps under the circumstances of ringing will be induced when the contacts on the clapper alternately make and break, thus causing the light pattern on the message lamp to emulate the audible pattern provided by the ringer.
However, as most people are aware, the somewhat accidental occurrence of the flashing of the telephone message light in synchronism with the ringing puts out a low level of light and augments, rather than substitutes for, the provision of an audible ringing signal to persons with normal hearing. Conversely, in applications in which the visual indication of telephone ringing is of primary importance, such as in the home of a deaf person, the prior art has adopted the expedient of allowing a detected ring signal to switch on an externally powered lamp of some variety.
Thus it will be understood that prior art high light output illumination devices for indicating telephone ringing have tended to be specialized and expensive. They have not been practical for use by a person of normal hearing due to this fact and because they flash in a manner which might not draw the attention of a person of normal hearing who is not used to keeping a look-out for such a flash. Thus, the provision of light-emitting telephone ringing indicators for persons of normal hearing has not been practical or popular.
Furthermore, in an environment particularly designed for a person with impaired hearing, it is necessary to distribute lights in several locations. In the example of the flashing of the message light on a hotel telephone, it is well known that the low light output of such devices (should someone attempt to use them in lieu of an audible signal) is such that it is virtually line of sight, and is not likely to be noticed under conditions of normal ambient light unless a person happens to be looking directly at the telephone set.
Thus, there is a need in the prior art for an inexpensive light-emitting indicator to alert a person that a ringing signal is present on the telephone line. Furthermore, it is highly desirable to provide such an indicator which will produce a light output signal which, by flashing pattern and intensity of light output, is likely to attract the attention of a person even if they are not looking directly at the phone and are in a location with normal ambient light. Similarly, the visibility of the signal from such a flasher in another room, when there is no direct line of sight to the light-emitting device, is a highly desirable property which has not been present to any appreciable degree in the prior art.
Lastly, such a device should be powered from the telephone line and thus be strictly an add-on device requiring no external source of power such as a 120 volt AC line or batteries.